Toxic Adenoma (Plummer’s Disease)
A toxic adenoma — also called Plummer’s disease — is a solitary thyroid nodule that produces thyroid hormone independently of the body’s control. It is one of the causes of an overactive thyroid.
Unlike Graves’ disease, the excess hormone comes from one nodule while the rest of the gland is suppressed.
Last medically reviewed: 15 November 2025
Key points
- A toxic adenoma is a single overactive nodule, not generalised thyroid overactivity.
- Blood tests show a low TSH with high free T4 and sometimes high free T3.
- A thyroid scan typically shows a hot nodule with suppressed activity in the rest of the gland.
- Treatment options include radioactive iodine, surgery or antithyroid medication.
What causes it
A toxic adenoma arises when a nodule acquires genetic changes that make its cells produce hormone continuously, without responding to TSH. Because the nodule is autonomous, the pituitary senses the excess hormone and switches off TSH production.
With TSH suppressed, the normal thyroid tissue around the nodule becomes inactive — which is why a scan shows one hot area and a quiet background.
Symptoms and diagnosis
Symptoms are those of an overactive thyroid: palpitations, weight loss, heat intolerance, tremor, anxiety and fatigue. Some people have few symptoms and are detected when a nodule is investigated.
Diagnosis combines thyroid function tests with ultrasound and a radionuclide scan. A hot nodule with suppressed surrounding tissue confirms the diagnosis. FNAC is usually not needed for a clearly hot nodule, because these are rarely malignant.
Treatment
Radioactive iodine is often the preferred treatment, because the suppressed normal tissue takes up little iodine and the dose is concentrated in the nodule. Surgery is an option for large nodules, compressive symptoms or when radioiodine is unsuitable.
Antithyroid drugs and beta-blockers can control the thyroid and symptoms while definitive treatment is arranged, but medication alone rarely cures a toxic adenoma.
What to expect afterwards
After radioiodine or surgery, thyroid function is monitored. Many people become hypothyroid and need levothyroxine, which is straightforward to manage. Nodule size usually shrinks over months after radioiodine.
When to seek urgent medical help
- Chest pain, fainting or a very fast or irregular heartbeat.
- Fever with agitation, confusion or vomiting — possible thyroid storm.
- Rapidly enlarging neck swelling or difficulty breathing.
This guidance does not replace emergency services. If you are seriously unwell, seek urgent medical care immediately.
Frequently asked questions
Is a toxic adenoma cancer?
No — a toxic adenoma is a benign overactive nodule. Hot nodules are rarely malignant, which is why biopsy is usually not required.
Can medication cure it?
Antithyroid drugs control hormone levels but rarely cure a toxic adenoma. Definitive treatment is usually radioactive iodine or surgery.
Will I become hypothyroid after treatment?
It is common after radioactive iodine or surgery, and is managed with levothyroxine. Monitoring after treatment identifies it early.
Can a toxic adenoma shrink on its own?
Spontaneous shrinkage is uncommon. Some nodules slowly enlarge, which is why treatment and monitoring are considered.
References & further reading
This page is based on established medical knowledge and guidelines from authoritative sources. Always consult a qualified clinician for personal medical advice.
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